Hydraulic pressure booster



Aug. 31, 1954 M. B. CONRAD HYDRAULIC PRESSURE BOOSTER Filed April 25, 1952 2 Sheets-Sheet l D, INVENTOR.

MqQr//v ,3. COA/e4 l BY I TroQ/VEVS Aug. 31, 1954 M. B. CONRAD HYDRAULIC PRESSURE BoosTER 2 Sheets-Sheet 2 Filed April 25, 1952 MAQT/N .Ba COA/@AD INVENTOR.

` BY MMM A b"v` mwfi NNW am Ww Nu u W w Am ww LM JM/f mm ww y un.. Rw l? R' Il!! T w Q 34W, R hm 7 J E R www@ rroe/vsys allow the `:duid to ably decreased, in order form, in which it may `arranged in position Patented Aug. 31, 1954 2,687,694 HYDRAULIC PRESSURE BOOSTER Martin B. Conrad, Downey,

Calif., assignor to Baker Oil Tools, Inc., Los Angeles, Calif., a corporation of California Application April 25, 1952, Serial No. 284,345

The present invention relates to apparatus for increasing the pressure of uid delivered to the apparatus from another source. An object of the present invention is to provide an improved apparatus which utilizes uid under pressureto increase or boost the pressure of such fluid to very high values.

Another object of the invention is to provide an apparatus which can be manipulated selectively to obtain increase in the pressure of fluid or `pass through the apparatus without increase inits pressure.

A further object of the invention is to provide an apparatus for increasing fluid pressure, which can be easily shifted between different relative positions, `despite the presence of high pressures, to effect an increase in the fluid pressure supplied to the apparatus or to eiect no increase insuch fluid pressure.

Still another object of the inventionis to provide a hydraulic pressure booster embodying seal rings to prevent leakage from the apparatus or between its various parts, and in which the pressure differential across the seal ringsis considerto avoid subjecting such rings to excessive hydraulic forces.

`This invention possesses many other advantages, andvhas other objects which `may be` made more clearly apparent from a consideration of a is shown in the drawings accompanying and `forming part of the present specification. It will now be described in detail, for the purpose of illustrating the general` principles of the invention; but it is to be understood that such detailed description is not to be taken in a limiting sense, `since the scope of the invention is `best dened by the appended claims.

Referring to the drawings: Figure 1 is a side elevation, on a reduced scale, o'fan apparatus embodying the invention, with a `small portion broken` away to provide a sectional view; Fig. 2 is an enlarged longitudinal section of the hydraulic booster apparatus, with the parts to effect no increase in the pressure of the fluid passing through the apparatus; i i I Fig. 3 is a view similar to Fig. 2, with the apparatus positioned to eect a boosting or `increase in the pressure of the uid supplied to the apparatus;

. Fig. 4 `is a` cross-section taken along the line 4*# on Fig. 3;

Fig. 5 is a fragmentary longitudinal` section,

be embodied. This form 18 Claims. (Cl. 103`52) `includes a rearward section on an enlarged scale, through the check valve portion of the apparatus.

The specic embodiment of the invention illustrated in the drawings has been particularly designed for providing fluid under exceedingly high pressures, for the purpose of testing articles, or other devices. It is to be understood, however, that theapparatus is capable of more general use than has just been indicated. As an example, it can also be used for pressure actuating purposes in general, in which an increase in the hydraulic pressure over that supplied by some other pressure source, such as a pump, is required.

As disclosed in the drawings, the hydraulic booster device includes a main `body ID that is generally elongate, and which may comprise several sections, in order to facilitate appropriate assembly of the apparatus. Thus, the main body I I terminating in an forwardly facing cam with a companion face enlarged head I2 carrying a surface I3 for cooperation or axial cam surface I4 formed on the rearward end of a cylinder I5. This cylinder is slidable longitudinally with respect to the body Ill in effecting selective shifting of the apparatus to the apparatus is operable to elect a substantial boost or increase in the pressure of the uid supplied to it. The rearward body section I2 is threaded into a forward body member IS, which, in turn, is threaded onto a nipple I'I that can be screwed into an outlet or discharge pipe I 8. A suitable inlet pipe I9 is threaded into the body head I2 at the rearward portion of the apparatus.

The cylinder I5 may be considered as having a slide valve portion also a uid motor Yaction of. the'spring: 32,

the outlet passage 26, the fluid under pressure can displace a suitable check valve 21 and continue its flow through the nipple passage 28 and on into the outlet pipe I8.

As disclosed in the drawings, and particularly Fig. 5, the check valve 21 includes a seat 29 provided by the forward end of the body section I I, which is engaged byy a valve head 30V centered with respect to the seat by a rearwardly projecting conical axial portion 3 I. A helical compression spring 32 bears against the head 30 and against a spring seat 33 in the rearward portion of the nipple I1, urging the head 33 constantly against its companion seat 291 Leakagebetween the seat 29 and head 3b is prevented by providing a suitable seal ring or gasket 34, which may take the form of a rubber O ring, inlanl annulargroove 35 in the head 36 and bearing against the seat 29. The fluid under pressure can shift the valve head 33 forwardly from its seat 29 against the but anyV tendency for such fluid to flow reversely backv into the outlet passage 26 is precluded by engagement. of the head 3,0; and' its sealring 34-.with theseat 23.

Leakage offiuid from the slide valve chamber 22 is'prevented by a suitable seal on each side of thev chamber; As illustrated"v in the drawings, a pair-of rubber O rings 35, 31f is mounted in suitable internal' grooves 38; 332 in the cylinder I5 andv slidably seal? against the periphery of the rearward body portion II. When' the cylinder is in the position disclosed in Fig. 2, it is quite apparent that fluid under pressure can flow be tween. the inlet an'd outlet ports 23, 24, and cannot leak longitudinally. in either longitudinal drection between the valve chamber and body portion IlI. When the cylinder I has been shifted, as:describedchereinafter, to the position illustrated in Fig. 3; theseal ringsv 36, 31 on opposite sides of' the chamber 22' will be disposed on opposite sides ofthe outlet port 24; and will prevent ilow ofv fluid. from the outlet port 24 to the inlet port 23; and also leakage ofiiuid through the valve chamber to the exterior of the latter;

The forward body section I5 has an outside diameter substantially less than the inside diameter ofthe sleeve or pump and motor portion 2| of the cylinder, which extends forwardly from the cylinderheadi or slide valve portion 2D that contains the valve chamber 22 and seal rings 36, 31. Such difference in diameter provides an annular space ilithrough which the annular skirt 41| ora piston 42v may slide, this piston having a rearward piston head 43 which is slidable within the annular cylinder space 44 that is dened be'- tween the'interior or the cylinder sleeve 2i and the external periphery of the rearward body member II. Leakage between the exteriorof the piston 42' and the cylinder skirt 2| is prevented by providingasuitable seal ring 45', such as a rubber olring, in an internall groove 46 in the sleeveZI, whichy slidably bears upon the periphery of the piston skirt 4I. Leakage between the inner sur- 'ace'of' the piston skirt 4t and the forward body portionl I3 is prevented by providing a plurality of"v seal rings 41, fifi, suchlas rubber O rings, in longitudinally spaced' grooves 43, 5) in the forwardbody. section I5, which slidably engage the inner surfaceof the piston skirt. Thread seals arealso provided to` prevent leakage ofA iiuid through the threaded joint 5I between the forwardand rearward body-:sections I6; II. As disclosed, these thread seals 52, 53 may bev rubber Y 01 rings, one of. which. 52 is` disposed in an internal groove- 5.4.in the forward body section I6 and bearing against the periphery of the rearward body section I I on one side of the threaded connection 5I, the other O ring 53 being provided in an external groove 55 in the rearward body section II on the other side of the threaded joint 5I and bearing against the inner surface of the forward body portion I 6.

A thread seal' 56 is also provided between the nipple I1 and the forward body' portion I6, consisting of a rubber O ring mounted in an eX- ternal groove 51 in the nipple and engaging the inner surface of the forward body portion I6 rearwardly of its threaded connection 53 with thenipple I1.

Leakage between the piston head 43 and the rearA body section II is prevented by providing a suitable seal ring 59, such as a rubber O ring, in an internal groove 56 in the piston head 43 which slidably bears upon the periphery of the body I I.

Itis tol be noted that the piston 42' separates the cylinder I5 andi body` It into two portions, one of which is a fluid motorv portion 6I rearwardly of the lpiston head 43, and the other of whichA is a fluid pump portion 62 forwardly of the. piston head; IIherey is an annular cylinder space E53 formed between the inner surface 64 of the piston skirt and the exterior 65 of the body portion I I, in:v which iluid may be contained, uidi passing into this cylinder space 63 through a lateral port 63 adjacent the rearward end of the forward body portion I6' and extending between the cylinder space 63 and the outlet bodlr passage 26".

Fluid under pressure can be supplied to the enlargeduid motor cylinder space 61 from the inletrpassage 25'and inlet port 23, when the cylinder I5'has been shifted to an appropriate position, such as the position illustrated in Fig; 3. Whendisposed inv this forward position, the valve seal rings 36, 31 are located on opposite sides-of the outlet port 24. However, at this time, a booster passage 53 in the cylinder is placed in communication with the inlet port 23, this passage having a suitable transverse branch or port 69 alignable with the inlet port 23 and allowing fluid under pressure from such port to iiow through thepassage 68 and into the enlarged cylinder space 51` rearwardly of the piston 42. Leakage of fluid from this booster passage 66 and inlet port 69, when the cylinder has been shifted forwardly to the position disclosed in Fig. 3, is prevented in aforward direction by the valve seal ring 36 engaging the body periphery. Leakage in a rearward direction is prevented by engagement of a suitable seal ring 10, such as a-rubber o" ring, with the periphery of the body I I, the ring beingV contained in an internal groove 1I in the cylinder I5.

Whenthe cylinder I5 occupies its rearward position on the body Iii, as disclosed in Fig. 2, the fluid motor cylinder space 61 and booster passage 68 are then opened to the atmosphere, so that fluid can bleed'from the cylinder space 61 and allow return movement of such return movement being limited by engagement ofthe piston with a transverse stop shoulder 12 provided on the body. The fluid in the motor cylinder spacelfcan flow through the booster passage 68 and into an annular area 1'3 between the inner surface of the cylinder I5 and a reduced diameter portion 14 of the body II, the fluidthen passing out through a transverse bleeder port 15 in the cylinder member to` the atmosphere.

the piston 42,

a companion threadedbore 18 in `leakage outwardly from the the handle being prevented by a suitable seal ring 19 in a groove 80 in the handle 16 engaging the e innersurfaceof a counterbore 8l in the cylinder.

ward direction. The body `verse cam face 84 on the body. A diametrically opposite high, low and cause the cylinder "illustrated in Fig. 3. The cylinder The cylinder I is shifted relative to the body `IIJ between the positions disclosed inFig. 2 and Fig. 3 by a cam device under manual turning eifort, that can be supplied 16 extending transversely from the cylinder. This handle has a threaded inner end 11 screwed into the cylinder, cylinder and around The cam device includes an axial cam`82 on the isengageable by a companion cam 83 at the rear portion ofthe cylinder I5 and facing in a rearhas a transverse cam or face, which terminates inran inclined 4rise portion 85, that extends to a transverse cam `surface or face 86 disposed forwardly of the other cam face 84.` The high cam face 86 of the body engages a companion low cam face 81 on the high cam face 89 on the cylinder, which, as disby a suitable handle body head I 2 facing in a `forward direction, which closed in Fig. 1, is then adjacent the low transi pair of such inclined cam faces 84-89 may be provided on the body I0 and also on the rearward portion of the cylinder I5.

` It is apparent that when the cylinder has been turned to the position illustrated in Figs. land 2,`the cylinder I5 occupies the rearward position with respect to the body I8, which allows the fluid to pass through the apparatus without its pressure being increased.` Upon rotating the cylinder I 5a partial revolution by grasping the handle 16, the coengaging inclined cam faces 85, 88 will body I8 to a position in which the high cam faces 86, 88 are in engagement, which will locate the cylinder in the position with respect to the body I5 can then be moved arcuately in the reverse direction, and the parts will return to their Figs.` 1 and 2 positions. Such return motion is positive through the pro- I5 to shift forwardly on the` vision of a stop and return screw 90 that is `threaded through the cylinder for reception within a helical groove 9| formed in the body I6 adjacent its head I2. This helical groove will have the same angle as the inclined cam surfaces 85, 88 that cause relative movement of the cylinder VI5 in a forward direction.

When the cylinder I5 is located on the body I I) in the non-pressure boosting position shown in Figs. 1 and 2, the fluid will pass from the inlet pipe I9 into the inlet passage 25 and thence through the inlet port 23 `22, continuing from the the outlet port 24 into the outlet passage 26, shifting the valve head 30 off its seat 29, and continuing on out .through the nipple passage 28 and the outlet pipe I8. Thus, the fluid under pressure in the inlet pipe I9, which may be supplied from any suitable source such as a pump (not shown), does not have its pressure increased in any particular.

Such fluid under pressure in the outlet passage 26 will pass into the pump cylinder space 63 through the transverse port 66, urging the piston 42 in a rearward direction and into engagement with its companion stop shoulder 12. This action `is permitted since the .fluid on the head end of the piston 42 can pass outwardly to atmosphere into the valve chamberV valve chamber through through the booster port 15.

`the fluid that is now to be discharged from the apparatus, the handle 16 is grasped, and the cylinder I5 is rotated so that the cam surfaces 85, 88 shift the cylinder forwardly of the body I8 of the apparatus, andto the position disclosed in Fig. 3, in which the booster passage 68 and fluid motor cylinder space 61 are placed in communication with the inlet passage 25 and its port 23, the valve chamber 22 then merely extending over the outlet port 24, with the seal rings 36, 31 disposed on opposite sides of the latter. One of the valve chamber seal rings 36 and the rearward seal ring 18, located on opposite sides of the booster passage port 69, are also on opposite sides of the inlet port 23, to prevent leakage therefrom. The uid under pressure in the inlet pipe I9 can then ilow through the inlet passage 25 and port`23 into the booster passage 68, and into the enlarged `cylinder space 61, urging the piston 42 in a forward direction within the cylinder I 5 and causing it to force the fluid in its cylinder space 83 of smaller area through the transverse passage 68 and into the outlet passage 26, from which such fluid under pressure will be forced around the check valve`38 and into the nipple passage 28 and outlet pipe I8. The fluid can be discharged until the piston 42 has been shifted .to its full `extent forwardly, which is determinedby engagement of the piston head 43 with the rearward end 92 of the forward body member I6.

When the cylinder and body parts I5, I 8 are area R of this latter `space 61 is much greater than the annular area S of the fluid pump cylinder space 63 measured between the inner surface 64 of the piston skirt and the periphery 65 of `the body I I. As a matter of fact, the annular area R yof the larger cylinder space 61 can be considere ably greater than the annular area S of the fluid pump cylinder space 63. i o

As disclosed in the drawings, the annular area R is approximately twice the annular area Si If it is assumed, merely by way of example, that the pressure of the fluid/in the inlet pipe I9 is 7,000

p. s. i., that will be the pressure of the fluid supplied to the iluid motorjcylinder space 61. Since the area Ris twice that of the area S, then space 63, and the pressureof such fluid when it is being discharged intothe outlet passage 2,6,"and from the apparatus, willbe 14,000 p. s. i., from which it is evident that a considerable boost or e increase in the pressure has been accomplished hydraulically through use of the fluid pressure in the inlet pipeIS itself. ofcourse, in obtaining such increase in pressure, it isrst necessary to illl the cylinder-space 63 in the pump portion of the apparatus, as well as the various passages 2S, 66 communicating therewith, with fluid, and thiscan be done very readily when the parts are located in their non-boosting position shown in Figs. l and 2. Thereafter, the shifting of the cylinder I5 with respect to the body I6 to the position shown in Fig. 3 Vwill enable the fluid under pressure in the inlet pipe I9 to effect a consider- `ableboost or increase in the pressure of the Huid the i skirt side of 7 inthe pump oylinderportionlt and the 66, 2G communicating therewith.

After.` the piston143' has moved to its forward limit,.to displace the-fluid from` the cylinder 63, the parts can again be shifted back to the position disclosed' in Figs. land 2. by grasping the handle 1|-ar1dzrotatingI the cylinder I5 a partial revolution, the. return screw 90 causing the cylinder to shift tofsuchrearward position. When thisoccurs, thepressure in theV inlet pipe I9I can then pass again through the inlet passage 25 and port 23; into the valve chamber 22, continuing through theI outlet port 24 into the outlet passage 2li,` and then through the pump body port 66- into the pump cylinder 6,3, acting against the piston 43 to urge the latter to its full rearward.l positionagainst the stop shoulder 1-2, as disclosed in Fig. 2.

Inl viewvof the comparativelyk high pressures to.` which the seal rings in the pump portion of the booster apparatus` are subjected, it is desired toV decreasev the pressure drop across certain of these rings. In-the example noted above, fluid at '1,000 p. s. i. is boosted to 14,000 p. s. i. During such boosting operation, the piston ring 59 is subjected to a '1,000 p. s. i. pressure at" the head endof the cylinder |5and to a 14,000 p. s. i. pressure in the pump cylinder 63 on its other side. Accordingly, there is a 7,000'p. s. i. pressure drop across this ring 59; which is not excessive, and which thering can withstand safely. Similarly, the seal vring 45 between the cylinder skirt 2| and the piston skirt 4| is subjected to the 7,000 pfsl i. pressure in the'fluid motor cylinder space 61, thepressure on the other side of this ring being atmospheric. Accordingly, there is only a '1,000Ap. s. i. pressure drop across this ring, which it cansafely withstand. However, the seal rings 4-1, 48 on the forward body portion IB are subjected on one side to the high pressure, which hasbeen. assumedv to be 14,000 p. s. i., the pressure on the other side of these seal rings ordinarily being atmospheric. Thus, the rings 41, 48 would be subjected to a 14,000 p. s. i. pressure differential, which might be excessive and which might cause displacement of some of the sealing ring material from the ring grooves 49, 50 in which they are located. Such excessive pressures are avoided in the presentcase, by an arrangement that will now bedescribed.

Thee rearward body portion has a passage 93- formed therein, opening into the cylinder space 61 ofV the fluid motor 6| adjacent the stop shoulderA 12, andy also opening into an annular space 94 betweentheforward and rearward body portions I'S, which communicates with a port 95 that extends to the periphery of the forward bodyY portion |6 between the longitudinally spaced seal' rings 41, 48. By virtue of this passage 93, the pressure in the motor cylinder space 61 is bled, or allowed to pass, to the clearance space between the forward body member It and the cylinder skirt 4| between the longitudinally spacedV rings 41, 48. Assuming the pressure in the motor cylinder space 61 to be 7,000 p. s. i., then this same fluid pressure is imposed upon paiSSageS both of the longitudinally spaced rings 41, 48.`

Accordingly, the high pressure in the pump cyllnderspace'of 14,000 p. s. i. on the rearward ring 41 is offset by the pressure of 7,000fp. s. i. on the other .side of this ring, which means ring 41 is being subjected only to a pressure differential of 7,000 p. s. i. The other ring 48 has the pressure of 7,000 p, s. i, disposed on one side of it'and atmospheric pressure on the other side.

that the Thus, the two rings 41,` 48` are fully capable of withstanding such pressure' differentials, which are considerably lower, namely only one-half. in the example specifically given, than the pressure tov which the ring 411 would otherwise have been subjected.

Similarly, the thread seal ring 52, which-is -subject to the high'v pressure in thepump cylinder space 03, will `have the pressure differentialacross it decreased tothe same extent as the outerring 41, inasmuch as the fluid from the` motor cylinder space 51 is capable of acting on its low pressure side. The other thread seal ring53l has the r1,000 lb. pressure imposed on one side and 14,000 p. s. i; pressure-imposed on its otherside, because of the fact that such high pressure will be present in the valveA chamber 91 betweenthe rearward body member land the threaded nipple |1. However, the pressure drop across this seal ring 53 is also only '1,000 p. s. i., which it can safely withstand.

It is, accordingly,. apparent that va hydraulic booster apparatus has been provided, in which the fluid under pressure canbe supplied to. the apparatus, and such pressure then increased t0 a considerable extent by utilizing fluid under pressure from the same source. The apparatus may be manipulated to either allow the fluid under pressure from the source tov pass through the apparatus, or to obtain a considerable increase in its pressure. Despite the output of comparatively high pressures, most of the seal rings of the apparatus are not subjected to such great pressure differentials, in. view of the use of some of the inlet pressure to offset the final outlet pressure. The cylinder and valve portions are easily shifted, the cylinder being under a substantially balanced condition so far as the inlet fluid pressure is concernedl when disposed in its non-boosting position shown in Fig. 2, which allows the cylinder I5 to be readily manipulated to shift it in a forward direction to its boosting position shown in Fig- 3. Return of the cylinder to its original position is also readily accomplished, inasmuch as any fluid under pressure within the motor cylinder space 61 will be effective in assisting return of the cylinder to its rearward non-boosting position. Despite the fact that such pressure forces are present when the cylinder is in the pressure boosting position, shown in Fig. 3, it still cannot shift to the rearward direction, in view of the engagement of the high cam faces 86, with one another, these faces being disposed in planes that are at right angles to the axis of the apparatus.

The inventor claims:

l. Hydraulic pressure booster apparatus, comprising a fluid motor, a fluid pump operatively connected to said motor to be actuated thereby, means providing an inlet for fluid to be supplied to said fluid motor and fluid pump, first passage means for conducting fluid from said inlet to said fluid pump, second passage means for conducting fluid from said inlet to said fluid motor, and shiftable valve means fluidly communicable with said inlet andsaid first and second passage means and selectively movable to positively prevent fluid ow between said inlet and first passage means while permitting fluid flow between saidinlet and second passage means or to positively prevent fluid flow between said inlet and second passage means while permitting fluid flow between said inlet and flrst passage means.

2. Hydraulic pressure booster apparatus, comprising a huid motor, a fluid pump operatively connected to said motor to be actuated thereby, means providing an inlet for fluid to be supplied to said fluid motor and fluid pump, first passage means for conducting fluid from said inlet to said fluid pump, second passagemeans for conduct ing lluid from said inlet to said fluid motor, and shiftable va -ve means iluidly communicable with said inlet and said first and second passageimeans and selectively movable to positively prevent iluid ow between said inlet and first passage means while permitting uid flow between said inlet and second passage means or fluid flow between said inlet and second passage means while permitting fluid ilowbetween said inlet and first passage means, the pressure actu-` atable area of said Huid motor being greater than the pressure actuatable areaof `said fluid pump.

3. `Hydraulic pressure booster apparatus, comprising a uid motor, a fluid pump operatively connected to said motor to be actuated thereby, means providing an inlet for iluid to be supplied to said iluid motor and Huid pump, first passage means for conducting fluid from said inlet to said fluid pump, said lirst passage means constituting both the inlet and outlet for said iluid pump, second passage means for conducting uid from said inlet to said fluid motor, and shiftable valve means `fluidly communicable with said inlet and said first and second passage means and selectively movable to positively preventiuid ow between said inlet and first passage means while permitting fluid flow between said inlet and second passage means or to positively prevent iluid flow between said inlet and second passage means while permitting fluid flow between `said inlet and first passage means.

4. Hydraulic pressure booster apparatus, comprising a body having an` inlet passage and an outlet passage, a cylinder on said body and having a portion spaced from said body to form an annular cylinder space, a piston movable longitudinally in said cylinder space and dividing said spaceinto a fluid motor portion and a fluid pump portion communicating with said outlet passage, passage means for conducting fluid from said inlet passage to said uid motor portion, and shiftable valve means operable to conduct fluid selectively between said inlet and outlet passages or between said inlet passage and passage means.

`5. Hydraulic pressure booster apparatus, comprising a body having an inlet passage and an outlet passage, a cylinder on said body and having a portion spaced from said body to form an annular cylinder space, a piston movable longitudinally in said cylinder spaceand dividing said space into a fluid motor portion and a fluid pump portion communicating with said outlet passage, `passage means for conducting uid from said inlet passage to said fluid motor portion, and shiftable valve means operable to conduct fluid selectively between said inlet and outlet passages or between said inlet passage and passage meanssaid .piston having an area subject to the pressure of fluid in said fluid motor portion which is greater than the areaof said piston for imposing pressure on the fluid in said `fluid pump portion.

6. Hydraulic pressure booster apparatus, comprising a body having an inlet passage and an outlet passage, a cylinder on said body and having a portion spaced from said body to form an annular cylinder space, a piston movable longitudinally in saidcylinder space and dividing said space into a fluid motor portion and a iluid pump portion communicating with said outlet passage,

to positively prevent` 10 passage means for conducting lluid from said inlet passage to said iluid motor portion, shiftable valve means operable to conduct iiuid selectively between said inlet and outlet passages or between said inlet passage and passage means,

and means for bleeding iluid from said passage means when said valve member has been shifted to a position conducting fluid between said inlet and outlet passages.

'7. Hydraulic pressure booster apparatus, comprising a body having an inlet passage and an outlet passage, a cylinder on said body and having a portion spaced from said body to form an annular cylinder space, a `piston movable longitudinally in said cylinder space and having a head dividing said space into a fluid motor portion and a fluid pump portion communicating with said outlet passage, said piston having a skirt secured to said head and slidable along said cylinder and body, the pressure actuatable area of said piston head on the skirt side of the piston being less than the pressure actuatable area of the other side operable to conduct fluid selectively between said inlet and outlet passages or between said inlet passage and passage means.

8. Hydraulic pressure booster apparatus, comprising a body having an inlet passage and an outlet passage, a cylinder slidable on said body and having a portion spaced from said body to form an annular cylinder space, a piston movable longitudinally in said cylinder space and dividing said space into a iluid motor portion and a uid pump portion communicating with said outlet passage, passage means for conducting fluid from said inlet passage to said lluid motor portion, valve means in said cylinder operable to conduct uid selectively between said inlet and outlet passages or between said inlet passage iand passage means, and means for shifting said cylinder longitudinally with respect to said body to dispose said valve means in such selective positions.

9. Hydraulic pressure booster apparatus, comprising a body having an inlet passage and an outlet passage, a cylinder slidable on said body and having a portion spaced from said body to form an annular cylinder space, a piston movable longitudinally in said cylinder space and fluid from said inlet passage to said fluid motor portion, valve means in said cylinder operable to conduct iluid selectively between said inlet and outlet passages or between said inlet passageand passage means, and coengaging camlmeans on said'body and cylinder for shifting said cylinder .10. Hydraulic pressure booster apparatus, comprising a body having an inlet passage .and an outlet passage,` a cylinder slidable on said body cylinder space, said cylinder cylinder and body, the pressure actuatable area aast-694 of said piston head on the skirt side of the piston being less than the pressureactuatable area of the other side of said piston head sub-ject to the pressure of fluid in said fluid motor portion, passage means for conducting iiuid from said inlet passage to said fluid motor portion, valve means in said cylinder operable to conduct fluid selectively between said inlet and outlet passages or between said inlet passage and passage means, and means for shifting said cylinder longitudinally with respect to said body to dispose said valve means in said selective positions.

11. Hydraulic pressure booster apparatus, comprising a body having an inlet passage and an outlet passage, a cylinder on said body and having a portion spaced from said body to form an annular cylinder space, a piston movable longitudinally in said cylinder space and dividing said space into a fluid motor portion and a fluid pump portion communicating with said outlet passage, passage means for conducting fluid from said inlet passage to said fluid motor portion, shiftable valve means operable to conduct fluid selectively between said inlet and outlet passages or between said inlet passage and passage means, longitudinally spaced sealing elements between said piston and body on the pump portion side of said piston, and means providing a fluid passage between said motor portion and the region between said sealing elements to subject said elements to the pressure of fluid in -said motor portion.

12. Hydraulic pressure booster apparatus, comprising a body having an inlet passage and an outlet passage, a cylinder on saidrbody and having a portion spaced from said body to form an annulai` cylinder space, a piston movable longitudinally in said cylinder space and dividing said space into auid motor portion and a fluid pump portion communicating with said outletpassage, passage means for conducting fluid Yfrom said inlet .passage to said .fluid motor portion, shiftable Valve means operablerto conduct uid selectively between said inlet and outlet passages or between said inlet passage and passage means, longitudinally spaced sealing elements between said piston and body on the pump portion side of said piston, and-meansfor conducting fluid from said inlet passage to the region between said .sealing elements to subjectv said-elements to the pressure of fluid in said inlet passage.

13. Hydraulic pressure booster apparatus, comprising a body having an .inlet passage and an outlet passage, a cylinder on said body and having a portion spaced from said body to form an annular cylinder space, a piston movable longitudinallyinsaid cylinder .space and dividing said space into a fluid motor portion and a fluid pump portion .communicating .with said .outlet passage, passage means for conducting fluid from said inlet passage to said fluid motor portion, shiftable valve means operable to conduct fluid selectively between said inlet and outlet passages or betweensaid inlet passage and passage means, longitudinally spaced sealing elements between said piston and body on vthe-pump portion side of said piston, and'emeans providing a fluid passage in said body between said `motor portion and the region Abetween said sealing elements to subject said elements to `the pressure of fluid in said motor portion.

14. Hydraulic-pressure booster apparatus, cornprising a body having an inlet passage and an outlet passage, a cylinder slidable onsaid body and having a portion spaced from said body to form an annular cylinder space, a piston movable 'longitudinally in said cylinder space and dividing said space into a uid vmotor portion and a fluid pump portion communicating with said outlet passage, passage means for conducting uid from said inlet passage to said fluid motor portion, valve means in said cylinder operable to conduct fluid selectively between said inlet and outlet passages or between said inlet passage fand passage means, means for shifting said cylinder longitudinally with respect to said body to `disposesaid valve means in such selective positions, and means for bleeding fluid from said passage means when said cylinder has been shifted to place said valve means in a position establishing communication between said inlet and outlet'passages.

15. Hydraulic pressure booster apparatus, comprising a body having an inlet passage andan outlet passage, a cylinder on said lbody and having a portion spaced from said body to form an annular cylinder space, `a piston movable longitudinally in said cylinder space and having a head dividing said space into a fluid motor portion and a iiuid pump portion -communicating with said outlet passage, said piston having a skirt secured-to said head and slidable along said cylinder `and body, the pressure actuatable area of said piston `head on the skirt side of the piston being less than the pressure actuatable area oi Vthe other side of said piston headsubject to the pressure of lfluid in said iiuid motor portion, passage means for conducting fluid from said inlet passage to said fluid motor portion, shiftable valve means operable to conduct fluid selectively between said inlet and outlet passages or between saidinletpassage and passage means, longitudinally spaced sealing elementsbetween saidbody and skirt, and means for conducting uid from said inlet vpassage to the `region between said Vsealing elements to'subject said elements to the pressure of 'fluid in said inlet passage.

16. Hydraulic pressure booster apparatus, comprising Va body having an inlet passage and an outlet passage, acylinder slidable on said body and having a portion spaced fromsaid body to forman annular cylinder space, a piston movable longitudinally in said cylinder space and dividing said space into a iluid motor portion and a fluid pump portion communicating with said outlet passage, passage means for conducting fluid from said inlet passage to said fluid motor portion, valve means in said cylinder operable to conduct uid selectively'between said inlet and outlet passages or between said inlet passage and passage means, means `for shifting said cylinder longitudinally with respect to said body .to dispose said valve means in such selective positions, `longitudinally spaced sealing elementsbetween said piston and body on vthe pump portion side of said -piston,.and means for conducting fiuid from said inlet passage Ato the region between said sealing elements to subject said elements to the .pressure of -ffluid in-said inlet passage.

,17. .-Hydraulicpressure booster apparatus, comprising :a uid motor, a fluid pump operatively connected to said motor pto be actuated thereby, means providing an inlet .for Afluid to be supplied to said :fluid `motor Aand fluid pump, first passage means .for conducting liuid from said inlet to said .fluid pump, secondpassage means for conducting fluid 4from said inlet to said fluid motor, third passage .means for bleeding uid from said second passage means, and shiftable Valve means fluidlycomm'unicable with said inlet landfsaid first, :second Aand third passage means 13 and selectively movable to place said second and third passage means in communication while positively preventing fluid flow between said inlet and second passage means and While permitting fluid ow between said inlet and nrst passage means or to permit fluid iiow between said inlet and second passage means while preventing fluid flow between said inlet and first passage means and between said second passage means and third passage means.

18. Hydraulic pressure booster apparatus, comprising a uid motor, a fluid pump operatively connected to said motor to be actuated thereby, means providing an inlet for Iiuid to be supplied to said fluid motor and fluid pump,` first passage means for conducting fluid from said inlet to said uid pump, second passage means for conducting uid from said inlet to said fluid motor, and a single valve control member `iiuidly References `cited in the nie of this patent UNITED sTATEs PATENTS Number Name Date 2,336,446 Tucker et al. Dec. 7, 1943 2,486,079 Tucker Oct. 25, 1949 2,579,670 Hjarpe Dec. 25, 1951 

